Indexable circular cutting insert

ABSTRACT

An indexable, invertable cutting insert has radially-oriented positioning segments on a front face of the insert and radially-oriented positioning segments on the back face of the insert. The radially-oriented positioning segments are shifted on the front face relative to those on the back face such that, when the cutting insert is engaged within the toolholder, the cutting segment utilized on the front face will never be directly opposite the cutting segment utilized on the back face. A toolholder system is made up of the cutting insert and a toolholder capable of securing and indexing the cutting insert.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to cutting inserts and is specifically directedto an invertable, indexable, circular cutting insert which, wheninverted, is designed to engage a cutting region longitudinally shiftedfrom a cutting region that may be utilized on the opposite side of theinsert. The invention also relates to a toolholder system utilizing thesubject cutting insert mounted within a toolholder, such as a millingcutter.

2. Description of Related Art

Milling cutters for cutting and shaping metal workpieces have been knownfor many years. Such milling cutters generally comprise a cylindricalcutting body having a plurality of insert seats spaced around theperiphery of the body. Cutting inserts are mounted within the insertseats and the insert seats are oriented so that the inserts mountedtherein will effectively cut a workpiece when a cutter body is rotatedalong a longitudinal axis. In one embodiment, circular cutting insertsare used within the pockets and indexed at such time as a portion of thecutting edge is worn. Oftentimes, such circular inserts are not onlyindexable, but also invertable. As a result, when a particular edge isworn, the insert may be inverted to engage a cutting edge on theopposite side of the insert. In previous designs, however, the portionof the cutting edge that engaged the workpiece on one side of thecutting insert was longitudinally opposite the portion of the cuttingedge on the opposite side which engaged the workpiece. As a result, whenthe cutting edge on the first side was utilized, the cutting edge andthe region adjacent to the cutting edge was subjected to hightemperatures and extreme conditions, which tended to degrade not justthe cutting edge, but the material in the region of the cutting edge.When the insert was inverted and the cutting edge longitudinallyopposite to the spent region was employed, the life of that cutting edgewas reduced because the material in the region proximate to that cuttingedge had been previously degraded through the use of the cutting edge onthe opposing side.

A need exists to better utilize the cutting edges on a circular,indexable cutting insert that is reversible to minimize degradation ofthe region proximate to a cutting edge when the cutting insert isinverted.

SUMMARY OF THE INVENTION

One embodiment of the subject invention is directed to an indexablecutting insert having a generally cylindrically shaped body with acentral longitudinal axis extending therethrough. The body has a frontface, an opposing back face, and a side wall therebetween. The body alsohas a front cutting edge at the intersection of the sidewall and thefront face and a back cutting edge at the intersection of the sidewalland the back face. A plurality of front positioning segments are on thefront face, wherein the front segments have centerlines and wherein thecenterlines of adjacent segments define evenly spaced radial angles RAabout the central longitudinal axis for indexing the insert within atoolholder. A plurality of back positioning segments are on the backface, wherein the back segments have centerlines and wherein thecenterlines of adjacent segments define evenly spaced radial angles RBabout the central longitudinal axis for indexing the insert within atoolholder. The centerlines of the back positioning segments, whenprojected along the central longitudinal axis through the body onto thefront face, bisect the radial angles RA defining the front positioningsegments.

A second embodiment of the subject invention is directed to a toolholdersystem for cutting a workpiece, wherein there is relative rotationbetween the toolholder and the workpiece. The toolholder system iscomprised of at least one cutting insert having a front face, anopposing back face, and a side wall therebetween. The cutting insertalso has a front cutting edge at the intersection of the sidewall andthe front face and a back cutting edge at the intersection of thesidewall and the back face. A plurality of front positioning segmentsare on the front face, wherein the front segments have radialcenterlines and, wherein the centerlines of adjacent segments defineevenly spaced radial angles RA about the central longitudinal axis forindexing the insert within a toolholder, wherein the front positioningsegments define a front pattern. A plurality of back positioningsegments are on the back face, wherein the back segments havecenterlines and, wherein the centerlines of adjacent segments defineevenly spaced radial angles RB about the central longitudinal axis forindexing the insert within a toolholder, wherein the back positioningsegments define a back pattern identical to that of the front pattern.The centerlines of the back positioning segments, when projected alongthe central longitudinal axis through the body onto the front face,bisect the radial angles RA defining the front positioning segments. Atoolholder has at least one seat for securably holding a circularcutting insert, wherein each of the at least one seats includes a bottomwall for engaging one of the front face and the back face of an insert,wherein the bottom wall further includes a plurality of receivingsegments positioned upon the bottom wall in the same pattern as thefront pattern and the back pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cutting insert in accordance with thesubject invention mounted within a milling cutter;

FIG. 2 is a front view of a cutting insert in accordance with thesubject invention;

FIG. 3 is a front perspective view of the cutting insert illustrated inFIG. 2;

FIG. 4 is a side view of the cutting insert illustrated in FIG. 2;

FIG. 5 is a back view of the cutting insert illustrated in FIG. 2;

FIG. 6 is a back perspective view of the cutting insert illustrated inFIG. 2;

FIG. 7 is a front view of the cutting insert in accordance with thesubject invention showing the positioning segments in schematic;

FIG. 8 is a back view of the cutting insert illustrated in FIG. 7;

FIG. 9 is a front view of a prior art cutting insert;

FIG. 10 is a side view of the cutting insert illustrated in FIG. 9;

FIG. 11 is identical to FIG. 7 and will be used to compare against FIG.12; and

FIG. 12 is a back view of the cutting insert illustrated in FIG. 11 andillustrated side-by-side with FIG. 11 to highlight the differences.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a toolholder system 10 for cutting a workpiece 15,wherein there is relative rotation between a toolholder 20 and theworkpiece 15. The toolholder system 10 is comprised of at least onecutting insert 30 and the toolholder 20. The toolholder 20 illustratedin FIG. 1 is a milling cutter that rotates about axis M.

Directing attention to FIGS. 2-6, the cutting insert 30 has a body 35with a front face 40, an opposing back face 50, and a side wall 60therebetween. At the intersection of the sidewall 60 and the front face40 is a front cutting edge 42. At the intersection of the sidewall 60and the back face 50 is a back cutting edge 52. A plurality ofpositioning segments 44A-D, on the front face 40, have radialcenterlines 45A-D extending from the longitudinal axis L, wherein thecenterlines 45A-D of adjacent segments 44A-D define evenly-spaced radialangles RA about the central longitudinal axis L for indexing the cuttinginsert 30 within the toolholder 20. The front positioning segments 44A-Ddefine a front pattern.

Additionally, a plurality of back positioning segments 54A-D on the backface 50 have radial centerlines 55A-D extending from the longitudinalaxis L, wherein the centerlines 55A-D of adjacent segments 54A-D defineevenly-spaced radial angles RB about the central longitudinal axis L forindexing the cutting insert 30 within the toolholder 20. The backpositioning segments 54A-D define a back pattern identical to that ofthe front pattern.

FIGS. 7 and 8 illustrate the cutting insert 30 in accordance with thesubject invention, whereby the positioning segments 44A-D and 54A-D areillustrated schematically and identify with the numbers 1-4 on the frontface 40 and the numbers 1-4 on the back face 50, respectively. Asillustrated in FIG. 5 with respect to the back segment centerline 55Aand representative of the other back face positioning segments, thecenterlines 55A-D of the back positioning segments 54A-D, when projectedalong the central longitudinal axis L through the body 35 onto the frontface 40, illustrated as phantom lines, bisect the radial angles RAdefining the front positioning segments 54A-D, as illustrated by theangle RA/2 between lines 55A and 45D.

FIGS. 9 and 10 illustrate a front view and side view of a prior artinsert, and the benefits of the subject invention will be described withrespect to this prior art insert.

The cutting insert 130 again has a front face 140 and a back face 150with a front cutting edge 142 and a back cutting edge 152 defined by theintersection of the sidewall 160 with the front face 140 and the backface 150, respectively. However, when the cutting insert 130 ispresented to the workpiece 115, the cutting edge 142 of the front face140 engages the workpiece between, for example, points A and B on thecutting edge 142. As a result, the primary wear to the cutting insert130 is on the cutting edge 142 between points A and B. In particular,the most severe wear occurs in the region of point A because, not onlyis that region the first to encounter the workpiece, but, furthermore,when the cutting insert is used for multiple machining operations atdifferent depths of the cut, point A is always exposed to thatworkpiece, while point B may or may not be exposed depending upon thedepth of the cut. Therefore, the region proximate to point A isrepeatedly heated and repeatedly subjected to extreme conditions. Thisregion of thermal degradation is represented by FR in FIG. 10. As can beseen in FIG. 9, cutting insert 130 is indexable and, as a result, may berotated to six different positions to expose the workpiece 115 to afresh cutting edge when the insert 130 is indexed.

However, the insert is also invertable and, in this prior art design,the positioning segments 144A-F are positioned at identical radiallocations about the longitudinal axis L as the positioning segments (notshown) on the back face 150. When the insert 130 is indexed to engage acutting edge 152 proximate to a front region FR that is alreadythermally degraded, then it is likely that that thermal degradation hasextended into the back region BR associated with the cutting edge 152 ofthe back face 150. As a result, the back region has already experienceda level of thermal degradation such that the cutting edge associatedwith that back region may prematurely wear.

The inventors have discovered that, in view of the thermal degradationassociated with the front region FR and the back region BR and thedegradation to a later-used cutting edge, it is possible to design thecutting insert such that the usable cutting edge is radially shifted.With the cutting edge shifted, then even though there is thermaldegradation on one side of the cutting insert, the thermal degradationon the opposite side of the cutting insert may be radially shifted sothat it does not affect the integrity of a cutting edge on the oppositeof the insert.

Directing attention to FIGS. 11 and 12 and expanding upon thedescription provided with FIGS. 7 and 8, the cutting edge 42 associatedwith the positioning segment 44A will produce a region FR ofdegradation. However, when the insert is inverted, the cutting edgedirectly opposite the front region FR will not be utilized, since thepositioning segments 54A-D on the back space 50 are shifted relative tothe positioning segments 44A-D on the front face 40. Therefore, the backregion BR, where the thermal degradation occurs, will also be shifted,such that, even though these regions still exist, they are radiallyshifted from the front region FR. Therefore, the thermal degradation hasa minimum impact on integrity of the cutting edge utilized on theopposite face of the insert.

Briefly returning to FIG. 1, the toolholder 20 has at least one seat 70for securably holding the cutting insert 30. The seat 70 includes abottom wall 72 for engaging one of the front face 40 and the back face50 of the insert 30 non-rotatable about the insert central longitudinalaxis L, wherein the bottom wall 72 further includes a plurality ofreceiving segments 75 positioned upon the bottom wall 72 in the samepattern as the front pattern of the front face 40 and the back patternof the back face 50. As a result, it can be appreciated that the cuttinginsert 30 is not only indexable about its longitudinal axis L, but,furthermore, is invertable, such that, at least with respect to cuttinginsert 30 illustrated in FIG. 1, there are eight useful cutting edgesprovided by this indexable, invertable cutting insert 30.

Redirecting attention to FIG. 1 and FIGS. 2-6, the front positioningsegments 44A-D and the back positioning segments 54A-D are projectionsextending from the respective front face 40 and back face 50. In thealternative, however, it should be easily envisioned and obvious to oneskilled in the art that the front positioning segments 44A-D and theback positioning segments 54A-D may be indentations extending into therespective faces 40, 50.

As seen in FIGS. 2 and 3, the front face 40 has a floor 47 spaced fromthe cutting edge 42 with a sloped wall 48 therebetween and, wherein thepositioning segments 44A-D extend from or into the floor 47, dependingupon whether they are projections or indentations. Furthermore, the backface 50 has a floor 57 spaced from the cutting edge 52 with a slopedwall 58 therebetween and the positioning segments 54A-D extend from orinto the floor 57, depending upon whether they are projections orindentations.

As generally illustrated in FIGS. 2 and 5, the positioning segments44A-D and 54A-D are generally U-shaped. Additionally, the positioningsegments are intended to rotationally locate and fix the cutting insertswithin the pocket of the toolholder and may have a number of differentshapes to achieve this goal. United States Patent ApplicationPublication No. 2011/0103905 assigned to the assignee of the presentapplication illustrates, among other things, a round cutting insert withanti-rotational features and is hereby incorporated by reference.Furthermore, as illustrated in FIGS. 2 and 5, the segments 44A-D includeindicia to uniquely identify each segment 44A-D on the front face 40 andeach segment 54A-D on the back face 50. As illustrated in FIGS. 2 and 5,the indicia may be numbers.

As shown in FIG. 7, the radial angles RA formed on the front face 40 areequal to the radial angles RB formed on the back face 50.

Directing attention to FIG. 1, the body 35 has a central bore 37extending therethough along the longitudinal central axis L toaccommodate a hold-down bolt 22 for securing the body 35 to thetoolholder 20.

As illustrated in FIGS. 2 and 5, there are four positioning segments44A-D on the front face 40 and four positioning segments 54A-D on theback face 50 of the body 35. Each segment forms an angle RA, RB of 90°with an adjacent segment on the respective face.

The prior art example, illustrated in FIG. 9, illustrates sixpositioning segments on the front face 140 and six positioning segments(not shown) on the back face 150. It can be appreciated, based on theforegoing discussion and in accordance with the subject invention, thatthe positioning segments on the front face 140 may be radially shiftedwith respect to the positioning segments on the back face 150 to shiftthe front region FR relative to the back region BR to minimize theimpact of thermal degradation from one side of the insert to the otherside of the insert. Although not illustrated, once again, it may beeasily envisioned and would be obvious to one skilled in the art toincrease the number of positioning segments to eight on each side,whereby each segment would form an angle of 45° with an adjacent segmenton the respective face and segments on opposite sides would be offset inaccordance with the subject invention.

It should further be appreciated that, while the subject invention hasbeen discussed with respect to a milling cutter, the subject inventionmay be applied to any number of toolholders utilizing indexable,invertable, circular cutting inserts. For example, a square shanktoolholder may be used.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of invention which is to be given the fullbreadth of the claims appended and any and all equivalents thereof.

The invention claimed is:
 1. A toolholder system for cutting aworkpiece, wherein there is relative rotation between the toolholder andthe workpiece, wherein the toolholder system is comprised of: a) atleast one circular cutting insert having: 1) a front face, an opposingback face, a side wall therebetween and a central longitudinal axistherethrough; 2) a front cutting edge at the intersection of thesidewall and the front face; 3) a back cutting edge at the intersectionof the sidewall and the back face; 4) a plurality of front positioningsegments on the front face, wherein the front segments have radialcenterlines and, wherein the centerlines of adjacent segments defineevenly spaced radial angles RA about the central longitudinal axis forindexing the insert within a toolholder, wherein the front positioningsegments define a front pattern; 5) a plurality of back positioningsegments on the back face, wherein the back segments have radialcenterlines and, wherein the radial centerlines of adjacent segmentsdefine evenly spaced radial angles RB about the central longitudinalaxis for indexing the insert within a toolholder, wherein the backpositioning segments define a back pattern identical to that of thefront pattern; and 6) wherein the radial centerlines of the backpositioning segments, when projected along the central longitudinal axisthrough the body onto the front face, bisect the radial angles RAdefining the front positioning segments; and b) a toolholder having atleast one seat securably holding the at least one circular cuttinginsert non-rotatable about the insert central longitudinal axis, whereineach of the at least one seats includes a bottom wall for engaging oneof the front face and the back face of an insert, wherein the bottomwall further includes a plurality of receiving segments positioned uponthe bottom wall in the same pattern as the front face and the back faceand wherein the at least one cutting insert is indexably secured to thetoolholder such that during a cutting operation, when mounted with thefront face exposed, a portion of the front face cutting edge isavailable to the workpiece and when the same insert is inverted with theback face exposed, a portion of the back face cutting edge is availableto the workpiece, wherein the front face portions and the back faceportions available to the workpiece are always radially shifted from oneanother.
 2. The toolholder system according to claim 1, wherein for theat least one cutting insert the front positioning segments and the backpositioning segments are projections extending from the respectivefaces.
 3. The toolholder system according to claim 1, wherein for the atleast one cutting insert the front positioning segments and the backpositioning segments are indentations extending into the respectivefaces.
 4. The toolholder system according to claim 1, wherein for the atleast one cutting insert the segments are generally U-shaped.
 5. Thetoolholder system according to claim 1, wherein for the at least onecutting insert the segments include indicia to uniquely identify eachsegment on a face.
 6. The toolholder system according to claim 5,wherein for the at least one cutting insert the indicia are numbers. 7.The toolholder system according to claim 1, wherein for the at least onecutting insert the radial angles RA formed on the front face have equalincrements to the radial angles RB formed on the back face.
 8. Thetoolholder system according to claim 1, wherein for the at least onecutting insert the body has a central bore extending therethrough alongthe longitudinal central axis to accommodate a hold-down bolt forsecuring the body to a toolholder.
 9. The toolholder system according toclaim 1, wherein for the at least one cutting insert there are fourpositioning segments on the front face and four positioning segments onthe back face of the body, wherein each segment forms an angle of 90degrees with an adjacent segment on the respective face.
 10. Thetoolholder system according to claim 1, wherein for the at least onecutting insert there are six positioning segments on the front face andsix positioning segments on the back face of the body, wherein eachsegment forms an angle of 60 degrees with an adjacent segment on therespective face.
 11. The toolholder system according to claim 1, whereinfor the at least one cutting insert there are eight positioning segmentson the front face and eight positioning segments on the back face of thebody, wherein each segment forms an angle of 45 degrees with an adjacentsegment on the respective face.